It is important here to recognise a fundamental difference between ancient and modern economies, and consequently between the strategic interests of ancient and modern states. Modern, industrialised economies cannot operate without access to certain natural resources - primarily oil, but also natural gas, rubber, and a range of minerals and metals. Without these, the entire system would grind to a halt. Unless alternative construction materials and sources of energy were found, the majority of people would lose their means of self-sufficiency, and society would collapse. It is therefore in the interest of states to secure all possible forms of access to these resources, even if supplies are already abundant.

The ancient Mediterranean world, on the other hand, was pre-industrial. The vast majority of people worked as farmers; the number one resource and form of wealth was land. In terms of strategic resources, the critical difference between this form of subsistence economy and modern globalised industry is that a subsistence farmer does not need any external resource. His production would certainly increase with access to livestock, specialist tools, engineering expertise, fertilisers, and so on, but he could theoretically do without them. Trade in natural resources was in some ways a fringe phenomenon - just wealthy elites toying around with the surplus of a system that ultimately functioned tolerably on its own.

This is not to say that trade wasn't going on. Indeed, evidence for systematic mineral mining goes back thousands of years, even in areas where there is no trace of large settlements; prestige items and the resources required to make them were clearly valued and exchanged all over the Mediterranean world. The obvious reason for the prominent role of the mythical Cedar Forest in Mesopotamian epics is that, in their desert floodplain, timber was one of the most precious and valuable resources. The prominence of bronze armour and weapons in Ancient Greece testifies to the importance of resource trade, since the copper and tin needed to make it were not available locally and had to come from regions as remote as Cyprus, Eastern Turkey, Spain, or even Cornwall. However, only the largest states (like the Assyrian Empire) had any hope of bringing such regions under their sway through military expansion. Conflicts among smaller states, if they had an economic motive at all, were far more likely to be about the most easily accessible and exploitable resource: agricultural land.

In that sense, ancient wars of conquest could easily be regarded as wars over natural resources. When Sparta conquered neighbouring Messene, probably in the 7th century BC, it absolutely served to increase the wealth and stability of Sparta by increasing its access to a strategic resource (land). Throughout the Archaic and Classical periods, agricultural production remained practically the only source of Spartan wealth, and their early expansion was all about getting hold of as much of it as possible. Most other Greek states were the same. Even the Persian Empire was seen as thriving on the agricultural surplus of its vast domains; the Athenian philosopher Xenophon argued that their prosperity was due to a combination of military power (securing their conquests) and careful husbandry (increasing the agricultural yield of their land). These two factors reinforced each other; if one or the other was lacking, the empire would collapse.

Land, then, was the most important natural resource in Antiquity, and it definitely was a cause for war. However, as states grew wealthier and societies more complex, other resources also became important. Throughout the Classical period, the population of Athens exceeded its territory's carrying capacity (since Attika was not great for agriculture); while they did some conquering across the Aegean to increase their available land, their main solution was to import grain from settlements around the Black Sea. As a result, the free flow of trade through the Hellespont became a particular strategic necessity for Athens. Threats to this region (and thereby to Athens' access to grain) were a reliable way to force a generally warlike Athens to sue for peace.

More generally, there is a clear connection in Antiquity between the complexity of states, the scope of military campaigns, and the need for natural resources. Modern scholars now assume that the introduction of the trireme - a potent warship, but also one that required much first-rate timber to build, and a large crew to operate - drove Greek states to develop their public finance systems and to invest hugely in securing access to timber and silver. Athens is the finest example of this. The Athenians were lucky enough to have a silver mine in their own territory, but the timber for their warships largely had to come from Northern Greece, either through trade with Macedon or through settlement in Thrace. Their transformation of the Delian League into an Athenian Empire in the mid-5th century BC included the quashing of a revolt to secure access to the mines of Thasos, as well as efforts to colonise the timber- and gold-rich Thracian coast opposite this island. When their main settlement in the area, Amphipolis, was liberated by the Spartans in 424 BC, they spent the ensuing century sending army after army into the region to try and get the city back. Ultimately, however, it was Philip II of Macedon who captured the city, and its silver and gold mines were the primary factor that enabled him to raise the professional army with which his son Alexander conquered the known world.